Default footer: Misalignment when many menu items are added

[beafialho]

Description
If we have a navigation with many menus, the columns look really awkward.

Step-by-step reproduction instructions

1. Check out default footer
2. Add at least six items to one of the navigations
3. Notice how the items look awkward because they're aligned at the middle

Expected behavior
The items within the column should be aligned at the top, not the middle.